What are the two meanings of monitor?

The word monitor has two main meanings as a noun and as a verb, though each has sub-senses. As a noun, a monitor is a device or person that watches or displays information. The most common noun meaning is a computer monitor, which is the screen that displays output from a computer. Another noun meaning is a person who watches or checks something, such as a hall monitor who ensures students behave, or a heart monitor device that displays vital signs. As a verb, to monitor means to observe, check, or track something over time to ensure it is working correctly or to detect changes. For example, to monitor progress means to keep track of progress regularly, and to monitor a patient's health means to observe vital signs continuously. So the two core meanings are a thing or person that watches or displays and the action of watching or tracking over time. Both meanings share the root idea of observing and informing, whether that is a screen informing you of data or a person observing a situation to maintain order or quality.